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Claude Sonnet 5.5 vs Kimi K2 Instruct

Claude Sonnet 5.5 leads the LLM Stats Score 58.0 to 21.9. Kimi K2 Instruct is 8.0x cheaper per token.

Anthropic · Moonshot AI · Updated for 2026

Which is better?

Claude Sonnet 5.5 leads the overall LLM Stats Score 58.0 to 21.9, ranking #3 overall.

In the 1 individual benchmarks reported for both models, Claude Sonnet 5.5 wins 1; this is a narrower head-to-head signal than the composite indexes.

On price, Kimi K2 Instruct is roughly 8.0x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Claude Sonnet 5.5 also accepts a larger context window (1,000,000 input tokens), making it the stronger choice for long documents and large codebases.

Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.

Choose Claude Sonnet 5.5

  • overall performance matters — it scores 58.0 and ranks #3 on LLM Stats
  • your work emphasizes reasoning and coding — it leads those capability indexes
  • you value its reported benchmark strengths — it wins 1 of 1 exact shared results
  • you process long inputs — it offers a 1,000,000 token context window
  • you want the most recent training data — it shipped Sep 2026

Choose Kimi K2 Instruct

  • cost matters — it's about 8.0x cheaper per token
  • you need open weights you can self-host or fine-tune

At a glance

The differences that matter most.

Claude Sonnet 5.5
Anthropic
Kimi K2 Instruct
Moonshot AI
Core performance indexes
LLM Stats Score
58.0
#3
21.9
#190
Reasoning
56.6
#3
22.0
#180
Coding
48.8
#2
12.4
#156
Agents
42.3
#3
-1.0
#183
Cost, coverage & limits
Benchmark wins
1 of 1
0 of 1
Input price
$2.00 / M
$0.50 / M
Output price
$10.00 / M
$0.50 / M
Context window
1,000,000
200,000

Capability indexes

Additional strengths measured across groups of related public benchmarks

2 shared
Index
Claude Sonnet 5.5
Kimi K2 Instruct
Math
36.9#34
22.2#143
Tool use
34.0#2
6.4#152
Conservative TrueSkill rating · higher is betterHow scores work

Individual benchmarks

47 reported for Claude Sonnet 5.5 · 38 for Kimi K2 Instruct

1 shared

Claude Sonnet 5.5 outperforms in 1 benchmarks (SWE-bench Multilingual), while Kimi K2 Instruct is better at 0 benchmarks.

Claude Sonnet 5.5 significantly outperforms across most benchmarks.

Fri Oct 02 2026 • llm-stats.com

Human preference

Blind head-to-head votes and playground preference scores

Pricing Analysis

Price comparison per million tokens

Kimi K2 Instruct costs less

For input processing, Claude Sonnet 5.5 ($2.00/1M tokens) is 4.0x more expensive than Kimi K2 Instruct ($0.50/1M tokens).

For output processing, Claude Sonnet 5.5 ($10.00/1M tokens) is 20.0x more expensive than Kimi K2 Instruct ($0.50/1M tokens).

In conclusion, Claude Sonnet 5.5 is more expensive than Kimi K2 Instruct.*

* Using a 3:1 ratio of input to output tokens

Lowest available price from all providers
Fri Oct 02 2026 • llm-stats.com
Anthropic
Claude Sonnet 5.5
Input tokens$2.00
Output tokens$10.00
Best providerAnthropic
Moonshot AI
Kimi K2 Instruct
Input tokens$0.50
Output tokens$0.50
Best providerFireworks
Notice missing or incorrect data?

Context Window

Maximum input and output token capacity

Claude Sonnet 5.5 accepts 1,000,000 input tokens compared to Kimi K2 Instruct's 200,000 tokens. Kimi K2 Instruct can generate longer responses up to 200,000 tokens, while Claude Sonnet 5.5 is limited to 128,000 tokens.

Anthropic
Claude Sonnet 5.5
Input1,000,000 tokens
Output128,000 tokens
Moonshot AI
Kimi K2 Instruct
Input200,000 tokens
Output200,000 tokens
Fri Oct 02 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Claude Sonnet 5.5 supports multimodal inputs, whereas Kimi K2 Instruct does not.

Claude Sonnet 5.5 can handle both text and other forms of data like images, making it suitable for multimodal applications.

Claude Sonnet 5.5

Text
Images
Audio
Video

Kimi K2 Instruct

Text
Images
Audio
Video

License

Usage and distribution terms

Claude Sonnet 5.5 is licensed under a proprietary license, while Kimi K2 Instruct uses MIT.

License differences may affect how you can use these models in commercial or open-source projects.

Claude Sonnet 5.5

Proprietary

Closed source

Kimi K2 Instruct

MIT

Open weights

Release Timeline

When each model was launched

Claude Sonnet 5.5 was released on 2026-09-28, while Kimi K2 Instruct was released on 2025-07-11.

Claude Sonnet 5.5 is 15 months newer than Kimi K2 Instruct.

Claude Sonnet 5.5

Sep 28, 2026

4 days ago

1.2yr newer
Kimi K2 Instruct

Jul 11, 2025

1.2 years ago

Knowledge Cutoff

When training data ends

Claude Sonnet 5.5 has a documented knowledge cutoff of 2026-06-01, while Kimi K2 Instruct's cutoff date is not specified.

We can confirm Claude Sonnet 5.5's training data extends to 2026-06-01, but cannot make a direct comparison without Kimi K2 Instruct's cutoff date.

Claude Sonnet 5.5

Jun 2026

Kimi K2 Instruct

—

Provider Availability

Claude Sonnet 5.5 is available from Anthropic. Kimi K2 Instruct is available from Fireworks, Novita.

Claude Sonnet 5.5

anthropic logo
Anthropic
Input Price:Input: $2.00/1MOutput Price:Output: $10.00/1M

Kimi K2 Instruct

fireworks logo
Fireworks
Input Price:Input: $0.50/1MOutput Price:Output: $0.50/1M
novita logo
Novita
Input Price:Input: $0.57/1MOutput Price:Output: $2.30/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?

Judge for yourself.

Run your own prompts against Claude Sonnet 5.5 and Kimi K2 Instruct side-by-side, then vote on the output you prefer.

Claude Sonnet 5.5
✓ Preferred
Kimi K2 Instruct
Open in Playground

FAQ

Common questions about Claude Sonnet 5.5 vs Kimi K2 Instruct.

Which is better, Claude Sonnet 5.5 or Kimi K2 Instruct?

Claude Sonnet 5.5 leads the LLM Stats Score 58.0 to 21.9. Claude Sonnet 5.5 is made by Anthropic and Kimi K2 Instruct is made by Moonshot AI. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

How does Claude Sonnet 5.5 compare to Kimi K2 Instruct in benchmarks?

Claude Sonnet 5.5 scores BenchCAD (with Python tool): 96.3%, ArXivMath (with tools): 95.2%, Global-MMLU: 92.1%, MILU: 91.6%, SWE-bench Multilingual: 90.3%. Kimi K2 Instruct scores MATH-500: 97.4%, GSM8k: 97.3%, CBNSL: 95.6%, HumanEval: 93.3%, MMLU-Redux: 92.7%.

Is Claude Sonnet 5.5 cheaper than Kimi K2 Instruct?

Kimi K2 Instruct is 4.0x cheaper for input tokens. Claude Sonnet 5.5 costs $2.00/M input and $10.00/M output via anthropic. Kimi K2 Instruct costs $0.50/M input and $0.50/M output via fireworks.

What are the context window sizes for Claude Sonnet 5.5 and Kimi K2 Instruct?

Claude Sonnet 5.5 supports 1.0M tokens and Kimi K2 Instruct supports 200K tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Claude Sonnet 5.5 and Kimi K2 Instruct?

Key differences include LLM Stats Score (58.0 vs 21.9), context window (1.0M vs 200K), input pricing ($2.00 vs $0.50/M), multimodal support (yes vs no), licensing (Proprietary vs MIT). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Sonnet 5.5 and Kimi K2 Instruct?

Claude Sonnet 5.5 is developed by Anthropic and Kimi K2 Instruct is developed by Moonshot AI.

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